(1) Field of the Invention
This invention relates to communication systems which employ electromagnetic signals in the infrared range. More particularly, this invention relates to communication systems which employ infrared transmission for bi-directional communication between stations which are not functionally disposed for direct infrared communication.
A number of recent technological advancements have employed infrared transmission to provide remote communication between a control station and an appliance or working device such as, for example, the familiar remote control employed, for tuning channels of a television set. Cordless telephones have employed infrared transmission to provide communication between a stationary transmitter/receiver and a portable telephone hand set which may be relatively freely moved about a given space within the transmission limit of the infrared transmission. The "IBM" PC Jr. computer employs infrared transmission to provide communication between the computer and the computer keyboard.
A principal factor in the increasing popularity of infrared transmission is the immunity of infrared transmission to common forms of interference which disrupt radio wave and ultrasonic transmissions. Moreover, immunity to unauthorized interception of infrared transmission is enhanced under conditions wherein a protected line of sight beam path is provided for the transmission. However, a fundamental drawback to the widespread use of infrared transmission is the requirement that the transmitter and receiver of the infrared transmission be functionally positioned within a common line of sight. Accordingly, the general objects of the present invention are to provide novel and improved systems for the transmission of infrared electromagnetic signal communication between stations wherein a direct common line of sight does not exist.
(2) Description of the Prior Art
Exemplary prior art transmission systems which employ infrared signal transmissions are typically limited to common line of sight transmitter and receiver configurations. U.S. Pat. No. 3,705,986 entitled "OPTICAL DATA TRANSMISSION SYSTEM" discloses a point-to-point digital transmission system which employs pulse modulated infrared beams. The system employs a pair of optical transceiver units which link one computer installation to another via a line of sight communication. The system employs an infrared emitting device and a photo detector at each of a pair of infrared transceivers in side-by-side relationship to provide parallel transmission paths between a pair of transceivers for providing high speed transmission data.
U.S. Pat. No. 3,927,316 entitled "WIRELESS SPEAKER SYSTEMS USING INFRARED LINK" discloses a unidirectional transmission system for transmitting audio signals from a fixed transmitter to a movable receiver. An infrared wireless speaker system employs an infrared wide band frequency modulated transmitter and receiver in combination with a conventional audio receiver and speaker system. A pulse rate modulated infrared light source is employed for transmitting an audio signal to remotely positioned speaker systems.
In U.S. Pat. No. 4,063,083 entitled "DATA COMMUNICATION SYSTEM USING LIGHT COUPLED INTERFACES" a data communication system is provided between spaced locations by interface assemblies positioned within a light path. Each interface assembly includes light sensitive and/or light emitting elements for extracting and/or supplementing light portions to a column of light passing along the path.
Cannon, Inc. of Tokyo, Japan has marketed an optical coupler Model X-721 which employs an infrared transmitter receiver within a desk mounted structure for facilitating infrared communication within a computer system. The infrared beam receiving and transmitting housing is mounted on a vertically orientated tubular structure having a rectangular pedestal. A modem connected to a telephone circuit may communicate with a computer via the coupler by means of infrared transmission. Infrared electromagnetic signal transmission represents on efficient mode for data communication.
U.S. Pat. No. 3,618,021 entitled "DATA COMMUNICATION SYSTEM AND TECHNIQUE TAGGING DATA DIFFERENT CLASSES", co-invented by the inventor herein, discloses a data communication technique adaptable for infrared signal transmission for transmitting information of two or more classes over a single channel or line. A packet switching technique is employed so that selected messages may be transmitted between a central computer site and various remote stations. Means are provided for selectively transmitting messages to a plurality of remote stations.